The present invention relates generally to medical devices and methods useful for batch sterile-filtering fluid prior to use as a replacement fluid in renal replacement therapies. More particularly, the devices and methods include using a filter such as a hemofilter first for sterile filtration of a replacement fluid to render the fluid sterile, followed by a renal replacement therapy that uses the sterilized fluid for infusion into a patient.
Patients undergoing hemofiltration, hemodialysis, hemodiafiltration, ultrafiltration, or other form of renal replacement therapy need replacement fluid, dialysate, or infusate which is free of biological contaminants. Given the large amount of sterile fluid needed by such therapies and the current method of spiking multiple bags of replacement fluid, dialysate, or infusate, there is a risk of touch contamination resulting in the introduction of biological contaminants into the fluids. Making the appropriate connections, then filtering the fluid greatly reduces this risk to the patient. It would be advantageous if the same equipment used in renal replacement therapy, such as hemofiltration, could be reconfigured for on-line decontamination of prepackaged solutions such as dialysate to produce the large volumes of sterilized replacement fluid required for the therapy.
Presently methods to produce volumes of dialysate from tap water are known, but require complex water purification/standardization equipment, since impurities and cleaning additives such as chlorine vary greatly in tap water from municipality to municipality and within a municipality over time. (See Twardowski U.S. Pat. Nos. 6,146,536 and 6,132,616.)
Moreover, dialysate solution, whether prepared online or prepackaged, while of the proper concentration for use as a sterile replacement fluid, is not deemed to be sufficiently free of pathogenic contaminants to allow the injection of such a fluid into a patient. In hemodialysis, the dialysate never enters the patient""s body, but instead flows past a semipermeable membrane that permits impurities in the blood to osmose through the membrane from the higher concentration blood to the lower concentration dialysate. Thus dialysate, intended for extracorporeal use only, is less expensive than solutions prepared as replacement fluids, which will be injected into a patient.
Attempts to render dialysate sufficiently sterile for use as a replacement fluid in hemofiltration and hemodiafiltration have focused on a continuous sterilization process that requires a separate dialysate filtration/purification apparatus that must be periodically purged and verified to provide sufficient constant flow of sterile replacement fluid required for hemofiltration. (See Chavallet U.S. Pat. Nos. 6,039,877 and 5,702,597.) Such devices are necessarily complicated and require separate pumping systems for the sterilization process.
However, if dialysate or other fluid of similar physiological make up could be converted to sterile replacement fluid in the same filter used for hemofiltration or hemodiafiltration, utilizing the same pumps, and without the need for periodic quality-controlled filter purging, a renal replacement therapy unit could be made significantly more simple for reconfiguration to a hemofiltration process to produce low cost sterile replacement fluid in situ. Moreover, the ready availability of pre-connected, disposable filtration and fluid pathway kits that have been sterilized and sealed by the manufacturer would significantly reduce the opportunity for touch contamination during the preparation of sterile replacement fluid.
The present invention provides devices and methods for producing sterile replacement fluid in a unit that is subsequently used for renal replacement therapy on a patient. The system can be used both to sterilize non-sterile fluid and to sterilize sterile fluid contaminated (e.g., by touch contamination) during connection due to improper technique. In a first embodiment, a system is provided to perform a method that includes the steps of providing a renal replacement therapy unit that has a filter with a membrane separating a waste side of the filter from a clean side. The membrane has a pore size smaller than the non-sterile and pyrogenic material to be filtered. The renal replacement therapy unit also includes a first container of a solution of suitable concentration for use as a replacement fluid that may include the non-sterile and/or pyrogenic material, or sterile fluid contaminated (e.g., by touch contamination) during connection due to improper technique. The first container is in fluid communication with the waste side of the filter. The unit also includes a second container that is adapted to hold sterile replacement fluid. The second container is in fluid communication with the clean side of the filter. A pump, generally the ultrafiltrate pump, is in fluid communication with the first container and the second container. The pump is capable of switching between a first direction that pumps fluid out of the first container and a second direction that removes waste from blood. A second pump, called a replacement fluid pump, pumps fluid out of the second container. The method further includes the step of running the pump in the first (reverse) direction to pump the solution of suitable concentration from the first container into the waste side of the filter. The solution from the first container is filtered through the membrane of the filter to trap the non-sterile and pyrogenic material on the waste side of the filter and produce sterile replacement fluid in the clean side of the filter. The sterile replacement fluid that flows from the clean side of the filter is collected in the second container. During therapy the pump switches to run in the second (forward) direction to pump waste from the blood. The sterile replacement fluid is pumped from the second container into the blood by a second pump. The sterile replacement fluid is used to perform renal replacement therapy on a patient.
Another embodiment is a pre-connected, sterilized fluid management kit for use in presterilizing replacement fluids prior to renal replacement therapy. The kit includes various disposable components of a renal replacement therapy unit. In one embodiment, the kit includes a fluid pumping and balancing system, a sterile fluid reservoir, a plurality of tubes conventionally used in a renal replacement therapy, and a replacement fluid container. Each of the plurality of tubes has a first end in fluid communication with the fluid pumping and balancing system and a second end releasably coupled to and in fluid communication with the sterile fluid reservoir. The replacement fluid container tube has a first end coupled to the fluid pumping and balancing system and a second end adapted to couple to a replacement fluid container. The kit is sterilized and packaged in a container at the time of manufacturing to prevent contamination prior to use in a renal replacement therapy unit.
Another embodiment is a system for batch sterilization of replacement fluid and renal replacement therapy using the sterilized fluid. The system includes a renal replacement therapy unit adapted to releasably receive a sterilized kit and a sterilized kit having preconnected disposable elements of the renal replacement therapy unit. The kit includes a fluid pumping and balancing system, a plurality of connectors, each having a first end coupled to the fluid pumping and balancing system and a second end adapted to releasably couple to the renal replacement therapy unit, a sterile replacement fluid container releasably coupled to the fluid pumping and balancing system through a plurality of tubes, and a tube having a first end coupled to the fluid pumping and balancing system and a second end adapted to releasably couple to a container of solution to be sterilized.
Another embodiment is a method for producing sterile replacement fluid in a renal replacement therapy unit. The method includes the steps of providing a renal replacement therapy unit, a sterilized kit that includes certain disposable elements of the unit, and a container of solution of suitable concentration for use as a replacement fluid. The unit is adapted to releasably receive the sterilized kit. The kit includes a plurality of tubes adapted to releasably couple to the renal replacement therapy unit, a preconnected sterile replacement fluid container and a tube having an end adapted to releasably couple to the solution container. The method further includes the steps of releasably coupling the sterilized kit to the renal replacement therapy unit, releasably coupling the tube to the container of a solution of suitable concentration for use as a replacement fluid, pumping the solution through the renal replacement therapy unit to sterilize it, and capturing the sterilized solution in the sterile replacement fluid container for use in renal replacement therapy.